1. Technical Field of the Invention
The present invention relates to a heat engine which heats and evaporates a working fluid, takes out energy from the vapor resulting from the evaporation in the form of mechanical energy, and then condenses the vapor for circulation, and which can be favorably used for an exhaust heat recovery apparatus.
2. Related Art
This type of heat engines, in general, use such an apparatus as a pump as disclosed in JP-A-H08-338207, for example. Specifically, in such a heat engine, an evaporation unit for evaporating a working fluid has a high pressure, while a condensation unit for condensing vapor (for restoring the working fluid) has a low pressure. The pump is used for circulating the working fluid condensed in the condensation unit into the evaporation unit. More specifically, such an apparatus as a pump is actuated using external energy, for pressurization of the working fluid in the condensation unit and for circulation of the pressurized working fluid into the evaporation unit.
As mentioned above, heat engines of the conventional art are configured to use such a mechanism as a pump to circulate a working fluid condensed in a condensation unit into an evaporation unit. Therefore, besides the external energy (heat energy) for heating and evaporating the working fluid, additional external energy is necessary for actuating the mechanism, such as a pump. Thus, the necessity of additional external energy unavoidably puts a limitation on the improvement of the output efficiency.